Patients with ocular toxoplasmosis, pars planitis, Behcet's disease, and chorioretinitis of unknown origin are being studied to determine the phenotype frequency of the HLA,ABO, and B-cell alloantigens. Because the B-cell alloantigens or DR antigens are thought to play a role in the immunologic response to antigens, these findings will complement other immune uveitis studies being conducted simultaneously. Restriction fragment analysis has begun to complement these HLA studies.